Heat olive oil in a 6-quart Dutch oven over medium-high heat. Rub salt all over pork shoulder and add to pot. Sear pork on all sides, then remove from pot, discard all but 1 tablespoon of oil from pot and return pork to pot, fat side up.
Add 4 cups of pineapple juice, sprinkle the oregano and cumin over pork fat cap, and simmer covered on low heat for 2 hours. Use 1 cup pineapple juice to baste pork occasionally as it continues to cook 1 more hour, covered.
Remove stems from dried guajillos and shake out excess seeds. Pour hot water over them to cover and allow to soak at least 30 minutes and up to an hour. Remove chiles from water and purée in food processor with garlic, habanero pepper and 1 cup pineapple juice. Set aside.
Remove bone (if any) and use two forks to pull/shred meat in pot. Add red chile sauce and simmer for 1 more hour, uncovered.
Toast ciabatta rolls and spread inside of each with 1/4 cup mashed black beans. Top with shredded pork, pineapple, a drizzle of Mexican Crema and chopped cilantro.